Abstract-Absorption, excitation and emission spectra of cadmium fluoride crystals doped with rare-earth ions were investigated. In contrast to alkaline-earth fluorides the absorption spectra due to 4f -5d transitions of Ce 3+ , Pr 3+ and Tb 3+ ions are broadened. No 5d-4f emissions were observed. These prove that 5d(eg) levels of rare earth ions lie in conduction band of CdF2 crystal. Emission spectra of Tb 3+ show the group of 4f-4f 5 D4-7 Fj lines in contrast to other alkaline-earth fluorides where emission due to 5 D3-7 Fj transitions is also observed. The absence of the emission is due to position of 5 D3 level within condution band.Among the all measured crystals doped with impurity ions (Pr, Nd, Eu, Ho, Tb, Tm, Yb, Ga, In or Mn), the CdF2 doped with Pr 3+ , Tb 3+ , or Mn 2+ ions have the highest light outputs under x-ray excitation.